The present invention relates generally to solenoid valves and more particularly to an electric vacuum regulator valve. Electric vacuum regulator valves as the name implies, operate on various input signals to generate a controlled output pressure signal. Quite often these vacuum regulators control the operation of other vacuum responsive devices such as vacuum motors. It is a known phenomenon that the generated controlled or output pressure of devices such as the present invention is a generally linear function of input current. Typical of the electric vacuum regulator art is U.S. Pat. No. 4,534,375 "Proportional Solenoid Valve" by Fox and European Patent Application EPA No. 84400623.9 "Electric Vacuum Regulator" by Mulder. The above references are illustrative of a relatively wide range of electropneumatic valves. In general, this class of electropneumatic valves operate in two distinct modes. The first, as illustrated by Fox and Mulder, is to establish a force equilibrium. More specifically, these valves are designed to generate an output pressure which varies between atmospheric pressure and a control pressure (which is typically a level established by a vacuum source such as engine intake manifold pressure). A movable valving element such as a flat plate is positioned within a pressure chamber and subject to a pressure force differential resulting from the interaction of atmospheric pressure forces and the controlled vacuum pressure forces. The disk is also located within and forms part of an electromagnetic circuit which upon activation establishes a electromagnetic-pressure force differential to control the output pressure signal as a function of an input variable, i.e. magnitude of current, duty cycle, et cetera. U.S. Pat. No. 4,005,733 "Pressure Control Valve"by Ridell, illustrates another electric vacuum regulating device which rather than establishing an equilibrium of electromagnetic and pressure forces across a movable valve, controls the output pressure by controlling the percent of time in each duty cycle that a particular valve seat (Ridell uses two) is opened in relation to the percent of time that it is closed.
Each of the above described devices must be calibrated such that the output or controlled pressure for a given input signal is a defined or definable quantity. With regard to Fox and Mulder, physical adjustment or calibration after assembly is required and performed in the following ways. Prior to adjustment a calibration point (or set point, operating point) has been determined such that for a given level of input current the output pressure should be a specified value. To obtain this value, in fact, requires that the air gap measured between a ferrous cylinder and a non-magnetic seat be varied to compensate for the stack-up of manufacturing tolerances to permit it the generation of a required magnetic force to be exerted on the valve element. In Fox this requires a relatively complicated calibration process in which his metal stator 16 is axially slid within a sleeve while his coil 18 is activated. Upon monitoring the output pressure the position of the metal tube 16 and sleeve 30 is fixed by welding, gluing or the like. In Mulder the air gap or orifice 30 is varied to similarly compensate for the stack-up of manufacturing tolerances. In contrast to the axial sliding used by Fox, Mulder uses a stator 36 which threadably engages a non-magnetic valve seat 50. Upon adjustment at the calibration or set point, the stator 36 with his coil 44 energized, is screwed in and out to vary the properties of the magnetic circuit in order to generate the desired controlled or output pressure.
As can be seen, the designs of Mulder and Fox require that in a production environment each and every vacuum regulator must be adjusted or calibrated. This procedure adds to the overall cost of the respective units.
It is an object of the present invention to provide an electric vacuum regulator that does not need post assembly calibration or adjustment. A further object of the present invention is to generate an output pressure signal proportional to an input current control signal.
Accordingly, the invention comprises: a pressure regulating valve comprising:
a magnetic circuit comprising a magnetic central portion having a fluid passage, adapted to receive fluid at a first pressure level; an annular, upraised magnetic valve seat coaxial with the central portion and disposed at and about one end of the central portion, the one end and valve seat disposed within a pressure chamber, the magnetic circuit further including first means, acted upon by the magnetic flux flowing through the magnetic circuit, to regulate the pressure within the pressure chamber corresponding with an input electrical signal, including a disk comprising, in at least a portion thereof through which the magnetic flux flows, a non-magnetic material of a given thickness facing the valve seat and a magnetic material secured to the non-magnetic material on a dimension thereof opposite the valve seat; means for biasing the disk toward the valve seat; means for communicating the pressure chamber to a pressure responsive device; first passage means for communicating fluid at a second pressure level to the pressure chamber.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.